Recently, in the field of the projection display devices, transmissive and reflective liquid crystal display devices and DMD display devices, which include micromirrors in an orderly array, are known as light valves that modulate light in order to produce image light signals. Among these projection display devices, decentered illuminating optical systems that illuminate reflective liquid crystal or DMD display devices from angles not perpendicular to the planes of the display devices are known. FIG. 7 shows an example of a projection display device having such a construction, using a reflective-type liquid crystal display panel 59 as a projection display device. This projection display device can be made very small, achieve high light efficiency, and is capable of providing an image with high image quality.
As shown in FIG. 7, the illuminating optical system includes a light source 50 that includes a light emitter 51 and a reflector 52 having a parabolic surface. The light source 50 emits a beam of substantially collimated light along an optical axis X defined by the axis of rotational symmetry of the parabolic reflector. An integrator unit 55 includes a first integrator plate that is a first fly-eye lens 53 that receives the illuminating light beam from the light source 50 and a second integrator plate that is a second fly-eye lens 54 that receives the illuminating light beam from the first integrator plate and that transmits the illuminating light toward a liquid crystal display panel 59. The fly-eye lenses of each of the two integrator plates includes a two-dimensional ordered array of microlenses. Each microlens has a similar cross-sectional shape to the effective image display area of the liquid crystal display panel 59.
The first fly-eye lens 53 divides the light having nonuniform brightness emitted from the light source 50 into a plurality of partial beams of light corresponding to the plurality of microlenses of the first fly-eye lens 53. It also converges each of the partial beams of light near the second fly-eye lens 54. The brightness of the partial beams of light after the division is more uniform that before the division.
The second fly-eye lens 54 includes microlenses individually corresponding to the microlenses of the first fly-eye lens 53. The second fly-eye lens 54 processes a plurality of secondary light source images formed by the first fly-eye lens 53 to form images on an illumination plane of the reflective-type liquid crystal display panel 59 via a condensing optical system 58 that includes lenses 56 and 57. On the illumination plane, more uniform illumination is realized compared to the illumination incident on the integrator unit 55 because partial beams from different microlenses of the second fly-eye lens 54 overlay one another. After being reflected from the liquid crystal display panel 59, the beam of light carrying the image information is projected onto a screen by a projection lens (not shown in FIG. 7).
Conventional illuminating systems, such as that described above, for providing more or less uniform illumination on the illumination plane using two fly-eye lenses are well known. However, in the above described illuminating system, although the two fly-eye lenses 53 and 54 are used to help provide uniform illumination on the liquid crystal display panel 59, there has been a problem that the distribution of the illumination is not adequately uniform because the two fly-eye lenses 53 and 54 are placed in tilted positions relative to the position of the liquid crystal display panel 59, as shown in FIG. 7. In the case of placement as shown in FIG. 7, a plurality of secondary light sources are formed by the first fly-eye lens 53 on a plane that is substantially perpendicular to the optical axis X. However, because the liquid display panel 59 is tilted relative to that plane, the distances between the plurality of secondary light source images and the liquid crystal display panel 59 vary depending on the location of the second light source images above or below the optical axis X, with those above being farther away than those below. As a result, the brightness of the illuminating light on the liquid crystal device varies significantly between the top and the bottom of the liquid crystal display panel 59.
The present invention relates to illuminating optical systems and projection display devices with uniform illumination of the reflective display devices using two fly-eye lenses in series preceding the reflective display devices. Additionally, the present invention relates to such illuminating optical systems and projection display devices that may use reflective display devices, such as reflective-type liquid crystal display devices or DMD display devices, with the illuminating optical systems arranged to provide more uniform illumination of the reflective image display devices.